An entrenched river is a river that is confined to a canyon or gorge, usually with a relatively narrow width and little or no flood plain, and often with meanders worn into the landscape. Such rivers form when the base level of erosion is rapidly lowered, so that the river begins downcutting into its channel faster than it can change course (which rivers normally do on a constant basis). This may occur due to tectonic uplift of the region, a lowering of the oceans, the collapse of a moraine-dammed lake downstream, or by capture of the river by another.
Meanders in these landscapes are collectively known as 'incised meanders and come in two forms. An ingrown meander is one where incision is slow and lateral erosion takes place resulting in an asymmetric valley. This resembles an exaggerated un-incised meander. The other sort is an entrenched meander, here rapid incision occurs creating a more symmetrical valley with a gorge like appearance. Both types are due to meanders becoming established before Rejuvenation.
Examples of incised meanders may be seen in the Snake River Canyon in southern Idaho, and in many canyons of the Colorado Plateau.
Famous quotes containing the words entrenched and/or river:
“In the case of our main stock of well-worn predicates, I submit that the judgment of projectibility has derived from the habitual projection, rather than the habitual projection from the judgment of projectibility. The reason why only the right predicates happen so luckily to have become well entrenched is just that the well entrenched predicates have thereby become the right ones.”
—Nelson Goodman (b. 1906)
“The murmurs of many a famous river on the other side of the globe reach even to us here, as to more distant dwellers on its banks; many a poet’s stream, floating the helms and shields of heroes on its bosom.”
—Henry David Thoreau (1817–1862)